I am sorry I am late to report this, but I just noticed that my update has been failing. I have a VERO 2 and was having the same sort of issue with the last big update, eventually wiping the VERO 2 and starting from scratch.
Seems like we are at that point again:
This failed at:
Err http://ftp.debian.org stretch/main armhf Packages
404 Not Found
Fetched 13.3 MB in 43s (302 kB/s)
W: Failed to fetch http://ftp.debian.org/debian/dists/stretch/main/binary-armhf/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
I also tried:
apt-get dist-upgrade --fix-missing
Which also failed with:
E: Failed to fetch http://apt.osmc.tv/pool/main/v/vero2-source-3.10.105-8-osmc/vero2-image-3.10.105-8-osmc_8_armhf.deb Hash Sum mismatch
E: Failed to fetch http://ftp.debian.org/debian/pool/main/t/tzdata/tzdata_2017c-0+deb9u1_all.deb Hash Sum mismatch
E: Failed to fetch http://apt.osmc.tv/pool/main/w/wireless-firmware-osmc/wireless-firmware-osmc_1.1.4_all.deb Hash Sum mismatch
E: Failed to fetch http://apt.osmc.tv/pool/main/m/mediacenter-addon-osmc/mediacenter-addon-osmc_3.0.654_all.deb Hash Sum mismatch
E: Failed to fetch http://apt.osmc.tv/pool/main/m/mediacenter-skin-osmc/mediacenter-skin-osmc_17.0.2-6_all.deb Hash Sum mismatch